(Present value of an annuity) What is the present value of the following annuities? a. $2,000 a year for 8 years discounted back to the present at 9 percent. b. $90 a year for 3 years discounted back to the present at 7 percent. c. $300 a year for 12 years discounted back to the present at 13 percent. d. $480 a year for 4 years discounted back to the present at 6 percent